1. Field of the Invention
The present invention relates to a liquid crystal display device, a terminal device, or a portable terminal.
2. Discussion of the Background
Recent increases in the size of liquid crystal display devices have expanded their market as display devices for notebook personal computers, monitors, and so on.
In conventional TN type liquid crystal display devices, the contrast of displayed image was highly dependent on viewing angle. In fact, the display is visible from only certain angles. This problem, however, is being improved through measures such as the use of viewing angle compensation film. This makes it possible to provide liquid crystal display devices with the same range of viewing angles as CRTs.
In U.S. Pat. No. 5,666,178 or U.S. Pat. No. 5,652,634, methods for broadening the viewing angle are disclosed. In these methods, in one pixel is provided with a plurality of sections, each with a different pre-tilt angle direction. Additionally, in Japanese Patent JP-A-9-5766, a method is disclosed in which a section is provided with a different pre-tilt angle direction in one pixel. In these disclosed prior art methods, the section with different pre-tilt angle direction is provided in one pixel for the purpose of broadening the viewing angle. The ratio between the areas of the sections with different pre-tilt angle directions is unique for all pixels, that is, one display, in order to prevent uneven areas from occurring. Therefore, these methods neither disclose nor suggest a method of providing a specified image that is visible when the image is viewed from a specified direction.
In Japanese Patent JP-A-61-51124 and Japanese Patent JP-A-61-51125 a device having plural display areas is disclosed. In this device, liquid crystalline molecular orientation directions on the alignment films are different on a single substrate. The display patterns of this device are typically numerical. In this device, some of the numbers (display patterns) can be seen from one direction, and the others cannot be seen from the same direction. The applications of this device intend that at least one numeral on a display pattern can be seen from a direction.
On the other hand, conversely to the above, other displays are preferably only visible from the front (i.e., they do not permit oblique viewing). This prevents secret or confidential documents from being viewed by people other than the user of the display device while the documents are being prepared or read in a public place. For example, this allows the user of such a display to read or write a document such as a personal letter, regardless of the presence of people around the user. Herein, such a technology will be denoted as “viewing angle narrowing technology.”
The viewing angle narrowing technologies that have been disclosed heretofore are a method of jointly using a liquid crystal display device having a liquid crystal layer for image display and a liquid crystal layer for phase difference control (JP-A-11-174489, JP-A-11-7045, JP-A-9-105958), a method of using a lens sheet (JP-A-11-84357 and others), a method of using a diffusing optical guide plate (JP-A-10-97199 and others), and so forth.
However, the above-described methods suffer from problems such as an increase in the number of parts and an insufficiently narrowed viewing angle.